The present invention relates generally to insulated thermocouple wire and, more particularly, to an improvement in the material surrounding and insulating a thermocouple wire, the material not including asbestos
Insulated wire used to "survey" or test a furnace, for example, to determine inside temperature of the furnace is a well-known product. Industrial furnaces, for example, may rise to extremely high temperatures requiring the survey wire to be sufficiently insulated. Previous insulated thermocouple wire has made use of asbestos for part of the insulation material. Due to the discovery that asbestos is a human health hazard, it is no longer acceptable as an ingredient for insulation. Asbestos has been used in combination with high temperature fiberglass to produce an insulation wrap around thermocouple wire. However, this combination of materials may not perform well above 1600.degree. F. Therefore, a need exists for thermocouple insulation material that does not include asbestos and which can perform at temperatures above 1600.degree. F.
It is an object of the present invention to fulfill the aforementioned needs. In the present invention, an insulated thermocouple wire is provided that can withstand temperatures of up to 2200.degree. F. for an extended period of time. In a typical example, two single wires or conductors are double wrapped with S-2 fiberglass insulation along with a percentage of thermal adhesive material to cover 100% of the bare metal with insulation material. Each single conductor, now insulated, is coated with a fiberglass binder and then cured in a drying chamber. The second conductor or wire is prepared in the same manner as the first. The two conductors are then arranged parallel with each other and braided together with high temperature fiberglass insulation. The entire braided outer jacket is coated with a fiberglass binder. The assembly is then cured in a heat chamber. The foregoing and other objects and advantages will become more apparent when viewed in light of the accompanying drawings and following detailed description.
The present invention can also be used to insulate other types of wire besides thermocouple wire.
For example, instrument hook-up wire can use the process of the present invention to provide an asbestos free, high temperature environment for the hook-up wire.